Welding is a manufacturing process used to join two or more pieces of metal by applying heat, pressure, or both. In many processes, the metal melts and forms a strong joint as it cools. Some methods use a separate filler metal, while others join surfaces without adding material.
The right welding process depends on several factors, including the type and thickness of the metal, the required strength, the work environment, production speed, and the appearance of the finished joint. In the United States, common welding applications range from automobile manufacturing and construction to pipeline work, shipbuilding, repair, and aerospace production.
Here are 12 important welding processes and how they work.
What is Welding?
Welding is a permanent joining process in which two pieces of metal join together to form one piece by heating the metals to their melting points. Additional metal, also called filler metal, is added during the heating process to help bond the two pieces together.
In general, it is a process in which two metal pieces, similar or dissimilar, may be joined by heating them to a temperature high enough to fuse the metals with or without the application of pressure and with or without the aid of filler material.
Welding Machine
A welding machine is used to create the heat and apply the filler metal. The filler metal is supplied to form the joint, either from the electrode itself or by filler material.
The temperature of the heat produced is of the order of 6000° to 7000°c. So, let’s discuss the different types of welding processes and how they are used in Industries.
Types of Welding Processes
1. Shielded Metal Arc Welding
Shielded Metal Arc Welding, commonly called SMAW or stick welding, uses a flux-coated metal electrode to create an electric arc between the electrode and the workpiece. The heat from the arc melts both the base metal and the end of the electrode, creating the weld. As the flux coating burns, it produces shielding gases and a layer of slag that protect the molten weld from contamination.
Stick welding is one of the most portable welding methods. The equipment can be carried to construction sites, farms, bridges, pipelines, and outdoor repair locations. It does not require an external shielding gas, which makes it more practical in windy conditions than processes that depend on a gas shield.
The electrode must be replaced as it is consumed, and the welder must remove slag between passes. This makes SMAW slower than some wire-fed processes. It also requires practice because the operator controls the arc length, travel speed, and electrode angle by hand.
SMAW can be used on carbon steel, stainless steel, cast iron, and certain alloys when the correct electrode is selected. It is especially useful for structural steel, maintenance work, heavy equipment repair, and field welding. Its flexibility and relatively low equipment cost have made it one of the most widely used welding processes.
2. Gas Metal Arc Welding.
Gas Metal Arc Welding, known as GMAW or MIG welding, uses a continuously fed solid wire electrode and a shielding gas. The wire melts into the joint while an electric arc supplies the required heat. Common shielding gases include argon, carbon dioxide, and mixtures of the two.
MIG welding is popular because it is relatively easy to learn and produces clean welds with little slag. Since the electrode is fed automatically through a welding gun, the operator does not need to stop frequently to replace a rod. This makes GMAW well suited to production work and long welds.
The process is often used with mild steel, stainless steel, and aluminum. It is common in automotive repair, metal furniture, farm equipment, fabrication shops, and manufacturing facilities. Operators can adjust the wire-feed speed and voltage to suit different material thicknesses.
One limitation is its sensitivity to wind. A strong draft can blow away the shielding gas and cause porosity or other defects. For this reason, MIG welding is usually performed indoors or in a protected area. The metal must also be reasonably clean because oil, rust, paint, and moisture can reduce weld quality.
GMAW may use short-circuit, spray, globular, or pulsed transfer modes. Each mode affects heat input, penetration, spatter, and the position in which the weld can be made.
3. Gas Tungsten Arc Welding.
Gas Tungsten Arc Welding, called GTAW or TIG welding, creates an arc between the workpiece and a nonconsumable tungsten electrode. The tungsten does not normally become part of the weld. A separate filler rod may be added by hand when necessary, although some joints can be made by melting the edges of the base metal alone.
TIG welding uses an inert shielding gas, usually argon or helium, to protect the weld area. It produces precise, clean, and attractive welds with very little spatter. The operator has excellent control over the arc and the amount of filler metal entering the joint.
This process is widely used for stainless steel, aluminum, nickel alloys, titanium, and thin sections of carbon steel. It is found in aerospace components, food-processing equipment, medical devices, bicycle frames, custom fabrication, and pipe work where weld quality is critical.
TIG welding is slower than MIG welding because the filler rod and torch are controlled separately. It also requires more coordination and concentration. The tungsten must remain clean and should not touch the molten weld pool. Contamination can make the arc unstable and introduce defects.
Although the process takes longer, it is valuable when appearance, dimensional accuracy, and corrosion resistance matter. A properly made TIG weld can have excellent strength and a smooth surface that requires little finishing.
4. Flux-Cored Arc Welding.
Flux-Cored Arc Welding, or FCAW, uses a continuously fed tubular wire filled with flux. The flux produces shielding gases and slag as it burns. Some FCAW wires also require an external shielding gas, while self-shielded wires produce their own protection.
FCAW is similar to MIG welding because both use a wire electrode that feeds continuously from a spool. However, the flux inside the FCAW wire allows the process to produce strong welds on heavier materials and in more demanding conditions.
Self-shielded FCAW is useful outdoors because it does not rely entirely on a separate gas supply. It is commonly used in construction, structural steel erection, ship repair, heavy machinery, and pipeline-related work. Gas-shielded FCAW is often used in fabrication shops where higher deposition rates and better control are needed.
The process can produce deeper penetration than many conventional MIG settings. It also works well on thicker steel and can tolerate some surface contamination. However, FCAW creates slag that must be removed, and it may produce more smoke and spatter than GMAW.
The choice of wire is important. Different wires are designed for specific metals, positions, strengths, and shielding methods. Operators must follow the manufacturer’s settings and welding procedure to prevent cracking, lack of fusion, excessive spatter, or trapped slag.
5. Submerged Arc Welding.
Submerged Arc Welding, or SAW, uses a continuously fed wire electrode beneath a layer of granular flux. The flux covers the arc and molten weld pool, so the arc is not normally visible during operation. The flux protects the weld from atmospheric contamination and helps reduce ultraviolet radiation and spatter.
SAW is often performed automatically or semi-automatically. It is particularly effective for long, straight welds on thick steel plates, pipes, pressure vessels, storage tanks, railroad components, and structural beams. Because the process can use high welding currents, it deposits metal quickly and produces deep penetration.
The blanket of flux also helps retain heat, improving efficiency. The finished weld can have a smooth appearance and consistent quality when the equipment is properly adjusted. Since the arc is hidden, however, the operator cannot watch it directly in the same way as with stick or TIG welding.
SAW is generally limited to flat or horizontal positions because the loose flux must remain over the joint. It also requires careful handling of unused flux. Moisture in the flux can contribute to hydrogen-related cracking or porosity, so storage and drying procedures are important.
This process is best suited to controlled production environments rather than small repairs or irregular field work. Its high deposition rate makes it an economical choice for large components with repetitive welds.
6. Plasma Arc Welding.
Plasma Arc Welding, or PAW, uses a constricted arc that passes through a small copper nozzle. The nozzle concentrates the arc and creates a high-temperature plasma stream. The process can use a nonconsumable tungsten electrode and shielding gas, much like TIG welding, but the focused arc provides greater energy density.
Plasma welding offers excellent control and can produce narrow, deep welds. It is used on stainless steel, titanium, nickel alloys, aluminum, and other metals in applications requiring accuracy. Keyhole welding, a specialized plasma technique, can penetrate thicker material in a single pass under controlled conditions.
The process is used in aerospace manufacturing, precision fabrication, instrumentation, and some pipe and sheet-metal applications. It may be operated manually, but automated systems are common when repeatability is important.
Compared with TIG welding, plasma arc equipment is more complex and usually more expensive. The operator must control torch height, gas flow, current, and travel speed carefully. A blocked or damaged nozzle can change the shape of the arc and affect weld quality.
PAW can produce clean welds with limited distortion, but proper joint preparation is essential. It is not usually the first choice for basic repair work because the equipment and setup requirements are greater than those of stick or MIG welding.
7. Resistance Spot Welding.
Resistance Spot Welding joins overlapping metal sheets by placing them between two electrodes. Pressure is applied, and an electrical current passes through the sheets. Resistance to the current generates heat at the contact point, forming a small fused area called a nugget.
The electrodes then continue applying pressure while the nugget cools and solidifies. No separate filler metal or shielding gas is normally required. The process is fast, repeatable, and well suited to automation.
Spot welding is strongly associated with automobile manufacturing, where hundreds or thousands of individual welds may hold a vehicle body together. It is also used for appliances, metal cabinets, electrical components, HVAC parts, and thin sheet-metal assemblies.
The quality of a spot weld depends on current, welding time, electrode pressure, material thickness, surface condition, and electrode shape. If the current is too low, the joint may be weak. If it is too high, the metal may burn through or expel molten material.
Resistance spot welding is most effective for overlapping sheets of similar thickness. It is less suitable for thick sections or joints that require continuous sealing. Regular electrode maintenance is necessary because the tips can wear, deform, or become contaminated during production.
8. Resistance Seam Welding.
Resistance Seam Welding is related to spot welding but uses rotating wheel-shaped electrodes instead of pointed electrodes. As the wheels travel along the joint, electrical current and pressure create a series of overlapping weld nuggets. The result can be a continuous or nearly continuous sealed seam.
This process is useful when a leak-resistant joint is needed. Common applications include fuel tanks, drums, radiators, mufflers, containers, and thin-walled tubing. It is also used in some aerospace and industrial manufacturing operations.
The welding current may be applied continuously or in timed pulses. Continuous current creates a more uninterrupted seam, while pulsed current produces overlapping individual welds and can reduce heat buildup. The correct setting depends on the material and the required seal.
Resistance seam welding offers high production speed and consistent results when the workpieces are accurately aligned. It does not require filler wire, flux, or shielding gas. However, the joint must generally be accessible to the electrode wheels, and the materials must have suitable thickness and electrical resistance.
Heat control is important because excessive heat can distort thin sheet metal. Wheel alignment, electrode pressure, travel speed, and cooling water flow all affect the final result. Poor control may cause leaks, incomplete fusion, excessive indentation, or burned edges.
9. Oxy-Fuel Gas Welding.
Oxy-Fuel Gas Welding uses the combustion of a fuel gas with oxygen to produce a flame. Oxyacetylene welding is the best-known version. The flame melts the edges of the workpieces and, when needed, a separate filler rod is added to complete the joint.
The operator can adjust the flame to create a neutral, carburizing, or oxidizing condition. A neutral flame is commonly used for many steel applications because it provides a balanced mixture of oxygen and fuel.
Oxy-fuel equipment is portable and does not require electricity, making it useful for maintenance, small repairs, farm work, and remote locations. The same equipment can also be used for heating, brazing, cutting, and loosening seized components.
Compared with arc welding, oxy-fuel welding usually produces a broader heat-affected zone and slower travel speed. This can increase distortion, particularly on thin sheet metal. It is also less efficient for thick structural materials.
The process can be used on mild steel, copper, brass, aluminum, and other metals with the right flame and filler material. Proper cylinder storage, leak testing, flashback protection, and ventilation are essential because oxygen and fuel gases create serious fire and explosion hazards.
10. Electron Beam Welding.
Electron Beam Welding, or EBW, uses a focused beam of high-speed electrons to generate heat. When the electrons strike the workpiece, their kinetic energy changes into heat and melts the metal. The process is often performed in a vacuum chamber, although some systems can operate at partial vacuum or in atmospheric conditions.
EBW can create very narrow welds with deep penetration and a small heat-affected zone. This helps reduce distortion and makes the process useful for precision components. It is used in aerospace, automotive powertrain parts, medical equipment, electronics, and specialized manufacturing.
Because the beam can be controlled accurately, electron beam welding can join difficult materials and components with strict dimensional requirements. It may also weld dissimilar metals in carefully designed applications.
The main disadvantage is equipment cost. Vacuum systems require chambers, pumps, fixtures, and specialized controls. The size of the workpiece may also be limited by the chamber dimensions. Operators need advanced training to manage beam focus, vacuum conditions, joint fit-up, and part positioning.
EBW is generally chosen when its precision and penetration justify the expense. It is not a typical process for general workshop repairs, but it plays an important role in high-value manufacturing where consistency and minimal distortion are priorities.
11. Laser Beam Welding.
Laser Beam Welding, or LBW, uses a concentrated laser beam to melt and join metal. The beam can be focused into a very small area, allowing high welding speeds and a narrow heat-affected zone. Filler wire may be added when the joint design requires additional material.
Laser welding is common in automotive manufacturing, batteries, electronics, medical devices, precision instruments, and aerospace components. It can produce clean, accurate welds and is well suited to robotic production lines.
Because the heat is concentrated, laser welding can reduce distortion compared with broader heat sources. It can also join small components and create precise weld patterns. Some systems combine a laser with an arc process to improve gap tolerance or deposition capacity.
The process requires accurate alignment and consistent joint fit-up. A large gap, surface contamination, or incorrect focus can reduce penetration and cause defects. Reflective materials such as aluminum and copper may require specialized laser systems and carefully selected settings.
Laser equipment is expensive, and the beam creates serious eye and skin hazards. Enclosures, interlocks, protective eyewear, and controlled access are essential. Like electron beam welding, laser welding is usually used when speed, precision, automation, and repeatability are more important than low initial equipment cost.
12. Friction Welding.
Friction Welding joins materials through heat generated by mechanical friction rather than by melting the entire joint. One workpiece rotates or moves against another under pressure. Friction raises the interface temperature, and the parts are then forced together to form a solid-state bond.
Because the materials remain mostly solid, friction welding can produce a small heat-affected zone and limited distortion. It can also join some combinations of metals that are difficult to fuse using conventional arc welding.
Several variations exist, including rotary friction welding, friction stir welding, and linear friction welding. Friction stir welding uses a rotating tool that travels along the joint and is widely used for aluminum panels, rail vehicles, aerospace structures, and transportation equipment. The tool softens and mixes the material without creating a conventional molten weld pool.
Friction welding is highly suitable for automation and repeat production. It can create strong, consistent joints when the machine settings, surface preparation, and component dimensions are controlled.
The process may require specialized machinery and carefully designed workpieces. It is less convenient for large, irregular repairs or locations where the equipment cannot be positioned properly. Still, its low distortion, strong joints, and ability to join dissimilar materials make it valuable in modern manufacturing.
Advantages of Welding Process
- A good weld will be stronger than the parent or base metal.
- Faster process compared to riveting and casting.
- Complete rigid joints can be provided with the welding process.
- Applicable to all metals and alloys.
- Complex shapes can be produced by welding.
- Welding equipment is portable and can be easily maintained.
- No noise is produced during the welding process, as in the case of riveting.
- The welding process requires less workspace in comparison to riveting.
- Any space of the joint can be made with ease.
Disadvantages of Welding Process
- Gives out harmful radiation, and fumes, and spotless (a sudden sprinkle of spark).
- Welded joints are more breakable, so their fatigue strength is less than the members joined.
- This results in distortion and induces internal stresses.
- It needs specific jigs and fixtures to hold metals properly.
- Skilled workers and electricity are needed for welding.
- The inspection of welding work is more complex and costlier than the riveting work.
Applications of Welding
The application of welding is so different and significant that it would be no exaggeration to say that there is no metal industry and no branch of engineering that does not use welding in one form or another, namely the automobile industry, ships, aerospace, and construction. It is majorly used for fabrication.
Some of the applications are:
- Shipbuilding
- Railway coaches
- Automobile chassis and bodybuilding
- Earthmover bodies
- Window shutters
- Doors, gates
- All types of fabrication work.
Wrapping It Up
As you know, welding is a strong joining process in which two metal parts join together to form one part by heating the metals to their melting points.
Some types of welding are made by machines and need costly specialized equipment. Welding is a faster method related to riveting and casting.